Microelectronic mechanical systems (“MEMS”) may be formed by etching features into one or more silicon wafers. Features may be etched in a silicon wafer using a number of techniques. One such technique is anisotropic deep silicon etching. For example, micro- or nanopillar arrays, accelerometers, complementary metal-oxide semiconductors, and micro- or nanofluidic devices may have one or more features that have been formed using anisotropic deep silicon etching.